It is well known to employ processing chemicals in the recovery of metals, minerals and rare earth elements. Metal ore processing in the past has employed various processing chemicals, some of which have had potential damaging effects to the environment. These processing chemicals may include mercury, cyanide, metal salts, alkali and alkaline metal salts, and strong acids.
A number of patents and literature references describe the use of chlorine as an oxidant in the removal of metals from ores. Chlorine gas has been previously used as a chemical oxidant, but it has been employed as a gas oxidant under positive pressure and elevated temperatures, which can result in unsafe operational discharge of chlorine to the atmosphere. In addition, the transport of liquid chlorine has become a safety transportation issue.
A number of conventional techniques combine the use of an aqueous chlorine solution, as well as hypochlorite which is another alternative chlorine-based chemical, in combination with the co-addition of a strong acid, such as HCl, as well as the addition of other additives such as chlorides (e.g., NaCl), metal salts such as iron compounds (e.g., FeCl3), and the addition of other oxidants such as ozone. The co-addition of the strong acids requires additional chemical expenditure costs and results in a dramatically greater volume of spent chemicals that need to be neutralized, processed, and recycled.
Other conventional techniques describe combining the use of cyanide with oxidizers or only use of chlorine in the gas form for the process of pre-treating the ore or additional treatment at high temperatures using chlorine and other gas Halogen oxidizers such as ozone.
In addition, a number of conventional techniques describe processes utilizing various mixing apparatus with the process oxidants employing stirring impellers or mixing blades which can consume significant amounts of energy as well as having established maintenance issues with equipment wear, erosion, and corrosion.
Thus, there is a need for an environmentally acceptable ore processing process that can utilize the oxidation potential of chlorine gas and/or other on-site generated oxidants and yet still provide environmentally acceptable methods for the safe recycle of the ore processing solution chemicals.